Dehydrogenation of secondary alcohols



United States Patent DEHYDROGENATION OF SECONDARY ALCOHOLS No Drawing. Application October '23, 1956 Serial No. 617,694

6 Claims. (Cl. 260-596) This invention relates to a catalyst comprising a metal oxide carried on a special kind of aluminum oxide support and to the use of this catalyst in the production of ',ketones by the dehydrogenation of secondary alcohols. More particularly it relates to the production of methyl ethyl ketone by the dehydrogenation of secondary butanol over zinc oxide-sodium carbonate catalyst'deposited on a porous alundum (alpha alumina) carrier.

The dehydrogenation of secondary alcohols to ketones is old. In the prior art, various catalysts, such as the near irreducible oxides of Mg, Cr, Mn, and the like, alone or in admixture with other oxides and supports, have been disclosed for such dehydrogenation, as have metals like coppenbrass, and zinc. More recently, the most successful commercial method for making methyl ethyl ketone (MEK) has involved dehydrogenation of secondary butanol using 94% ZnO-6% Na CO coated on lumps of commercial calcined coke. However, in several respects even this catalyst has shown shortcomings. First, the non-uniform particle size of the coke leads to non-uniform heat transfer, resulting in local hot spots, carbonization of the catalyst, and thus shortercatalyst life. Second, the non-porous surface of the coke leads to inferior coating of the ZnO-Na CO slurry, resulting in powdering of the active catalyst and hence non-uniform activity level and shorter catalyst life. The use of alumina, or aluminum oxide (A1 0 as' a catalyst or as a catalyst support is a well-known, highly developed art. Basically three major classifications of alumina are distinguished: The hydrated low temperature forms, the nearly-anhydrous intermediate forms, and the anhydrous high temperature forms. The first of these three, alumina hydrates, are commonly found in natural form as gibbsite (hydrargillite), bayerite,bohmite, and diaspore, and in the pure form have been correspondingly assigned names more directly related to their structure: respectively, alpha alumina trihydrate, beta alumina trihydrate, alpha alumina monohydrate, and beta alumina monohydrate. These hydrates have limited catalytic applications as such and are more valuable as starting materials for the production of the aforementioned intermediate forms of alumina.

Among many catalytic applications, these activated aluminas have been used in catalysts to catalyze certain dehydrogenation reactions such as that of cyclohexane to benzene. However, aluminas suitable for these dehydrogenation reactions have not provedsuccessful in the 1..

preparation of ketones by the catalytic dehydrogenation of alcohols, for they invariably have caused extensive dehydration of the molecule as well as the desired dehydrogenation.

Finally, upon further calcination of the intermediate forms of alumina at temperatures generally above 2000 F. but below the melting point of alumina (about 3700 F.), or upon the direct calcination of beta alumina monohydrate at temperatures as low as 800 F., the high temperature forms of alumina, particularly alpha alumina, are obtained. Alpha alumina is distinctive from other aluminas in its unique hexagonal crystal structure, in its non-absorptivity, in its very low surface area, and hence in its low activity. When calcined at temperatures as high as 2000 F. (inherent with its production from all other lower temperature forms except bet-a alumina monohydrate), alpha alumina has a surface area usually below 1 meter /gram and not more than 10 mP/gm. On the other hand, other aluminas previously discussed, and certainly those used for catalytic applications, have surface areas varying between about and 450 mF/gm. Alundum is probably the best known name for alpha alumina, and for purposes of clarity, this word Alundum shall be used hereinafter. specifically in place of alpha alumina.

Further information regarding the various types of alumina, their properties, and their preparation can be found in Technical Paper No. 10, A. S. Russell, Aluminum Company of America (1953).

The main object of this invention is to provide a catalyst for the dehydrogenation of alcohols to ketones which will give longer catalyst life. Another object of the invention is to improve the above type of dehydrogena-' tion by providing a catalyst having more uniform activity and longer life. A further object of the invention is to provide an alumina-type catalyst which will successfully cause dehydrogenation of alcohols to ketones without appreciable dehydration. Other objects of the invention will become apparent as the details of the invention are disclosed hereinafter.

It has now been discovered that Alundum, unlike other previously used aluminas, can be used successfully as a carrier for dehydrogenation catalysts such as ZnO- N21 CO in the dehydrogenation of an alcohol to a ketone. Actually, for the purposes of this invention, the surface area of the Alundum should be at least below 10 m. /gm., preferably below 5 m. /gm., and most desirably below 1 mF/gm. The Alundum prepared by the lower temperature calcination of beta alumina monohydrate has a greater area and must be further heated to temperatures above about 2000 F. Because of the properties of Alundum mentioned above, especially its nonabsorptiveness and low surface area, successful use of such alumina as a catalyst support was highly unexpected. At the same time, such use of Alundum was found to avoid the aforementioned disadvantages that characterized the previously used catalysts carried on a coke support.

The catalyst of the present invention is prepared by first water-washing a commercial grade Alundum, such as tabular-Alundum, then intimately mixing Na CO powder with a commercial grade of powdered ZnO and trang sa e 1 o 20%. 0 he il 0 892. F?

3 96% ZnO and 8 to 4% Na CO Such preferred ratios necessarily require mixing approximately 9.2 to 9.6 parts of ZnO and 0.8 to 0.4 part of Na CO in each blending step with a total of about 100 to 200 parts of Alundum.

It is to be noted that the results shown above are similar for runs 1 and 3 using the coke and the Alundum supports, except the new catalyst used in run 3 exhibits better activity. This superiority is definitely greater in About 5 to 10, usually about 8, parts of H are used magnitude than could be attributed to the slightly higher in'each blending step. The'cat'alyst is preferably heated temperature used in run 3. Inaddrtxon the two catato reaction temperatures prior-to use as a dehydrogenalysts are comparable as to selectivity to MEK and H 0. tion catalyst in this invention. However, the decisive superionty of the Alundum sup- The dehydrogenation of secondary alcohols is effected ported catalyst over the coke supported catalyst became in the presence of the above described catalyst at tem- 1O strikingly apparent upon conclusion ofthe runs when perat res in the range of 600 to 950 F., preferably the catalyst, in each case, was removed from the reactor. 700 to 850 F. The reactionis usually carried out at In the case of the support of the present 1 r1vent1on, the tmospheric pressure, although a range from about 'oj catalyst was removed in the same umform size and shape to atmospheres is feasible. Instead of'operating at which it possessed when it was charged to the reactor, vacuum pressures, a similar effect may be obtained by- Whereas the PP f catalyst'wheh removed c011 diluting the reagents with inert gases such as nitrogen tained a Substalltlal fraction III the form of fines, or light refinery gases, e.g. CH and thelike. The volu p Thus. the new catalyst qould e recharged for metric alcohol feed rate for the i v ti may y further. reaction while a substantial portwnof the old between 0.75 and 5.0 volumes of liquid alcohol per catalyst required l volume of catalyst per hour, preferably 1.5 to 3.0 The catalyst of ru 2 gave completely unsatlsfactqry v./v./hr. When the reaction exists at the preferred conresults- The cohdltlohs' 0f h p and Volumetric ditions of temperature, pressure and feed'rate, an alcohol feed were p low lhtefltlonahy tofmvent excesslve conversion usually greater than 90% is achieved, together dehydration, thus a y CODVBTSIOH tOYMEK W118 with a product l i i to MEK i excess f 95% caused. Howeveryeven at this low temperature and con-. and a ele ti it t H 0 l h 1% hi low sale? version the selectivlty to H O 1s stillvery much greater. tivity to H 0 indicates that dehydration is negligible, a than that when the new catalyst comhlhahoh of surprising finding when it is considered that conventional used- Hence, cohfinhs the wehfikhowhfact-that activated alumina could not be used because of its tend the use achvhted alumlhas for catalyst ency to cause excessive dehydration of the alcohol. At Supports obvlohsh lmprachcal for such alcohol the same time the uniformity in size and theporosity of hydrogehahoh reachohs' a structure of the new catalyst allows it to overcome the The example refers to the Prodhchoh of ih'Q two di ad t of h coke Support; namely, new secondary butanol. However, .the advantages of th1s mu if h tr f d powdering of the cokegsup ventlon maybe similarly, applied to the dehydrogenation ported ZnONa CO catalyst. The elimination of these Qt ,sehohdary alcohols to Produce h' h two disadvantages is evidenced by the fact that when Typlcal shhhhr examples would be the Produchoh of the catalyst of the present invention is removed from the stone from p p PrOpyl butyl ketone from. 4- reactor there is no crushed material present, Whereas h or 1 h Preparahoh of C3 to C8 or evteh he the coke supported catalyst is removed-there is a higher carbon containing ketones from the corresponding large Portion in powdered form secondary alcohols. The example also refers to.the use To further emphasize the nature and advantages of the 40 of ZnO Na2CO3 catalyst but h advahtages of h present invention, the following specific example is set novel i' support can be liltlllzefhslmllarly' wuh forth. However, it should be understood that the invenother.metal'oxldes known for achvhy as dehydro tion is not limited to the example. Unless otherwise $52 3 catalysts Such as those Mgi Cr! ,V f,, f percentages are given throughout v Having thus described the nature of the invention, the. true scope 1s particularly pointed out in the appended. Example claims.

What is claimed is:

Secondary butanol was dehydrated at hlgh tempera- 1. A process for Producing ketones by thedehydmgcm thl'es to Produce M first 2; h Standard ation of a lower secondary alcohol of three to eight-car- 2 3 011 calclhed Coke; Secondly uhlhg the Same bon atoms which comprises contacting said alcoholatacatalyst on a COIIVGII IIOHaI actlvated alumina (eta alutemperature between and F with a d i ly and thlrdly 118mg 2 s. tahulaf h reducible metal oxide dehydrogenation catalyst for said dhm which was formed as Pebbles Inch dehydrogenation deposited on an alpha alumina carrier Size y calcining alpha 3131mm} mohohydlate at p having a surface area of less than 5 meters gram. tures of about 2200 F. A mixture of- 9.4 parts of ZnO 2 A process for producing ketones by the dehydrogen; and P of z s' mlXed In a slurry with 3 ation ofa lower secondary aliphatic alcohol of 3. to 8 PartS Of Water, then mixed h 150 p the carbon'atoms which comprises contacting said alcohol at (him, and dried temperature F Another a temperature between 700 to 850 F. with a-zinc'oxide Coat of part8 Z110, P -Q r '-P 2 dehydrogenation catalyst for said dehydrogenation dewas then added by the same procedure-and the-mixture posited on alpha alumina of surface area lessthanl was redried at 350 F. for use in the synthesis. The meter /gram as a support wherein said oxide constitutes following data were obtained: 5 to-25. weight percent of the total catalyst.

. Selectivity, wt.

Av; Converpercent Run Catalyst strap Vs/V-Ihl'. slon' M.E.K. mo

1'. Standaid'94% Zn0'6% NazC'O'r 745' 1.67 37-3 98-99 2 94%? ail-6% NarOOr on eta 500 1.60 18 5.1 3; 94% r io fi% NarCOa on tabular 775 1.59 96-7 97 0.6

Alundum.

aeeeaea 3. A process according to claim 2 wherein said alpha alumina is prepared by the calcination of aluminum oxide at temperatures above about 2000 F. and below the melting point of said aluminum oxide.

4. A process according to claim 2 wherein the active catalyst constituent comprises a mixture of 90 to 98 parts by weight of ZnO and correspondingly 10 to 2 parts by weight of Na CO 5. A process for producing methyl ethyl ketone which comprises passing secondary butanol at a temperature between 600 and 950 F. over a metal oxide catalyst which dehydrogenates the secondary butanol to the ketone selected from the group consisting of the oxides of cerium, magnesium, manganese, chromium, beryllium, iron, and zinc deposited on alpha alumina of surface area less than 1 meter /gram.

6. A dehydrogenation process for producing methyl ethyl ketone which comprises passing secondary butanol at a temperature between 700 and 850 F., substantially atmospheric pressure, and a liquid volumetric feed rate between 1.5 and 3.0 volumes of butanol per volume of References Cited in the file of this patent UNITED STATES PATENTS 1,895,528 Taylor et al. Jan. 31, 1933 2,331,292 Archibald et al Oct. 12, 1943 2,472,493 Schneider et al. June 7, 1949 2,480,520 Thacker Aug. 30, 1949 2,504,497 Charles et al. Apr. 18, 1950 2,633,475 Mottern Mar. 31, 1953 2,794,053 Altreuter et al May 28, 1957 2,800,518 Pitzer July 23, 1957 

1. A PROCESS FOR PRODUCING KETONES BY THE DEHYDROGENATION OF A LOWER SECONDARY ALCHOL OF THREE TO EIGHT CARBON ATOMS WHICH COMPRISES CONTACTING SAID ALCOHOL AT A TEMPERATURE BETWEEN 600* AND 950* F. WITH A DIFFICULTLY REDUCIBLE METAL OXIDE DEHYDROGENATION CATALYST FOR SAID DEHYDROGENATION DEPOSITED ON AN ALPHA ALUMINA CARRIER HAVING A SURFACE AREA OF LESS THAN 5 METERS 2/GRAM. 